PCB or Hybrid Printed Circuit Board is a PCB which makes use of dissimilar materials with the intent of optimizing electrical performance and improving system reliability which is focused towards the RF applications of high-frequency. One of the biggest challenge that are generally faced by the manufacturers of this type of PCB is managing the varying co-efficient of thermal expansion comprising of dissimilar circuit materials both during the time of component assembly and PCB fabrication.
There are certain unique mechanical features of high frequency PCBs. When you manage the RF and electrical properties of hybrid circuits, you have to come across a number of challenges. There are a number of unique mechanical features that are truly desirable by the PCB designers. A few of the specific items include.
Odd Shape Board Outlines:
Most of the times a hybrid PCB must fit into the unique enclosures or some other space and there are times when RF PCB outline has a number of different turns and twists. It is true that routing the outline of this circuit is not a difficult task but it is a super-sensitive process. So, a hybrid design is to be dealt with carefully. Most of the times PTEE materials are very soft and the speeds and feeds need to be slowed down for making the edges crisp.
One other factor to take care of is the fact that the drill has to be constantly monitored as the material is much more aggressive. It means you can possibly get out of the tolerance when the bit wears down excessively at the time of this process. One important thing to keep in mind is that RF products are made of woven materials and can fray out easily if they are not cut carefully.
Internal Pockets or Controlled Depth Rout Patterns:
Hybrid multilayer PCB is manufactured using multiple lamination cycles while the others are done by using a controlled-depth routing process of some sorts usually a laser-cutter or a router bit. Both of these processes have their set of specific challenges which can add cost and intricacies to any hi-speed PCB design. Normally, these designs include a blend of PTEE laminates and FR-4 materials.
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